Inside his laboratory at Medical College of Georgia, Brian Condie can turn mouse embryo cells into brain cells or heart cells. His research and that of others may one day allow adults to grow new cells and turn around disorders such as Parkinson's disease.
Dr. Condie, an assistant professor in the Institute for Molecular Medicine and Genetics at MCG, is one of hundreds of researchers looking for the key to stem cells. Their promise, and their potential for ethical conflicts, was the subject of a special section in last week's edition of the journal Science.
Stem cells are like cell factories. They are able to reproduce themselves while also generating cells that can become essential to the body, such as red blood cells or skin cells. Recently, researchers discovered stem cells in the adult brain and found that these cells could be manipulated to become neurons.
What role the cells play in the brain is still unclear. Some researchers in the Science article speculate that the cells could play a role in forming new memories; others raise the hope of regeneration. That dream underlies much of the excitement about stem cells.
"The hope is we'd be able to take a particular type of stem cell and then either implant that stem cell directly into damaged tissue and have these cells differentiate and develop into tissues that can repair that tissue," Dr. Condie said. One of the causes of Parkinson's disease may be the failure of brain cells to continue making the essential neurotransmitter dopamine.
In the future, "you may be able to recover stem cells from an individual, grow them up in cell culture and then return that population of stem cells to the same person, which eliminates the problem of graft rejection. So one of the hopes is that adult neural stem cells in particular will be a source for (this type of) transplantation, which will get around the whole tissue rejection issue."
That process is already used with blood stem cells, which can be harvested before high-dose chemotherapy, stored and then injected back into the patient to replace the stem cells in the bone marrow destroyed by the chemotherapy.
But there are still some problems that must be overcome. In early clinical experiments, the stem cells have not survived well once reintroduced, Dr. Condie said.
"Maybe we don't understand enough about the interactions between that stem cell and its environment to encourage it to differentiate and develop properly in that environment and make the right connections," Dr. Condie said. "The other complexity in the brain is developing the right connections."
In some early animal experiments, however, the neural stem cells once injected went straight to the source of damage and formed cells to replace the damaged ones. Taking a cue from developmental biology, where embryonic stem cells have long been studied, Dr. Condie and other researchers are trying to pin down how those cells are signaled to play the right role.
By using a particular growth factor, Dr. Condie can grow nerve cells from his mouse embryonic stem cells.
"But if I had treated them in a slightly different way, I would have ended up with plates full of cardiac muscle cells," Dr. Condie said. "These are from an early enough stage of development that they have the potential to go on and make anything."
The key will be learning how to manipulate the adult stem cells, he said.
"In a lot of situations in development, in differentiation of cells, the cells take their cues from neighboring cells, so they're dependent on signals coming from their environment to decide what pathway to take," Dr. Condie said. "We just need to understand more about what these signals are and how these cells talk to each other, what signals are present at certain times."
The early research has caused some excitement on Parkinson's-related Web sites, said Jeana Bartlett of Augusta, who suffers from the disease.
"I don't know what the prognosis is, if it would ever be a viable option for Parkinson's people, but I've heard it's looking that way," Mrs. Bartlett said. What is attractive about stem cell treatment is that cells from her own body would be used to fight her disease, she said.
"So there is no ethical thing involved with baby pig embryos," she said.
Congress is currently debating whether to allow National Institutes of Health-funded research to use human embyronic tissue, a debate the scientific community is encouraging. Dr. Condie uses mouse tissue, which, he said, is comfortably out of that debate.
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